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freebsd Softupdates and the ldm queue

Jim,
I recall your saying you were running your Unidata software on freebsd.
We just acquired a freebsd box too for our Unidata software using
freebsd 4.7 release. Tom recommended I check in with you to see if you
had any advice on Softupdates.

Our box has 3 scsi drives and I've made 2 slices on the second, a 3 GB
for the ldm queues, the rest for the Unidata software home(s), and on
the 3rd drive I've got a slice for swap, the rest for ldm's /data.

My question is: is it advantageous or no for the queue partition on the
second drive to have Softupdates turned off, while all other partitions
(except /) have Softupdates implemented? My limited understanding of
Softupdates is that it improves I/O rates by 'cache'ing file metadata
updates to disk, so that the ondisk metadata changes are allowed to 'get
behind' corresponding data writes at times until I/O activity will allow
them to catch up. Does this argue for or against Softupdates on the
queue file system? 

On Mon, 2003-03-17 at 19:49, Unidata Support wrote:
> >From: "Neil R. Smith" <address@hidden>
> >Organization: TAMU
> >Keywords: 200303130136.h2D1aoB2022568 LDM FreeBSD
> 
> Hi Neil,
> 
> >I've got my ldm.pq on a separate 3GB partition on a different disk from
> >my /data partition .. thinking that would make things a little faster.
> >I'm using Softupdates on my filesystems, but thinking about this queue
> >partition, do you think I should not enable Softupdates for it?
> 
> If the only thing you have in the file system is your LDM queue, I
> would not have Softupdates turned on for it.
> 
> >What config/partitioning have you found optimal on freebsd? (I'm using
> >freebsd 4.7 release).
> 
> Since we are not (yet) doing anything but moving data with our FreeBSD
> box (we are using it in LDM stress testing and it is sailing along
> happily), it is hard to say if the queue would be better in its own
> partition.  It is not on a separate partition on our system.   For
> reference, we are using 10K rpm IBM SCSI disks in our FreeBSD box.  It
> is also a dual 1 Ghz processor system with 4 GB of RAM.  We run our LDM
> with a 2 GB queue, but that is mainly since we are using it in testing
> movement of all IDD data to multiple (7) downstream machines.  FYI, it
> is moving an average of 31 Mbps of data to downstream machines, and has
> been doing so for just over 6 days now.  After we stop our stress
> testing series, we will be converting this FreeBSD box into our data
> ingest/decode machine for GEMPAK, McIDAS, and the netCDF decoders and
> as an ADDE server for THREDDS testing.
> 
> Sorry I couldn't provide more insight into disk tuning.   We may have
> more to say after the machines takes up decoding and data serving
> duties.  You might want to touch base with Jim Koermer of Plymouth
> State <address@hidden> to see what he did before he put a
> RAID on one of his FreeBSD systems.
> 
> Tom
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-- 
Neil R. Smith, Comp. Sys. Mngr.         address@hidden
Dept. Atmospheric Sci., Texas A&M Univ. 979/845-6272 FAX:979/862-4466